The invention relates to controlling fluid flow in conduits such as shunt tubes or other types of alternate conduits.
To complete a well, one or more formation zones adjacent the wellbore are perforated to allow fluid from the formation zones to flow into the well for production to the surface. Perforations are typically created by perforating gun strings that are lowered to desired intervals in the wellbore. When fired, perforating guns extend perforations into the surrounding formation.
In producing fluids from a formation, particulate materials such as sand may be produced with the formation fluids. Such particulates may damage the well and significantly reduce production and life of the well. Formation fluids containing particulates may act as an abrasive that wears and erodes downhole components, such as tubing. In addition, production of particulates such as sand may create voids in the formation behind the casing which may result in buckling of or other damage to the casing. The flow of the production fluids may be insufficient to lift the particulates from the well, which may result in buildup of the particulates in the well. In addition, particulates produced to the surface are waste products requiring disposal, which may be costly.
Various methods and devices for reducing or eliminating sand and other particulate production have been developed. Gravel packing of the formation is a popular method for controlling sand production. However, other sand control mechanisms may also be used. Although there are variations, gravel packing essentially involves placing a sand screen around the section of the production string containing the production inlets. This section of the production string is aligned with the perforations. A slurry of gravel in a viscous transport fluid is pumped into the annulus between the sand screen and the casing. The deposited gravel blocks the formation particulates, such as sand, from flowing into the production tubing. However, formation fluids are allowed to enter the production string for flow to the well surface.
A major issue associated with gravel packing is obtaining substantially uniform distribution of the gravel over the entire interval to be completed. Poor distribution of gravel is often caused by the loss of liquid from the gravel slurry into the more permeable portions of the formation, which causes creation of gravel "bridges" in the annulus before all of the gravel has been placed. These bridges block further flow of the slurry through the annulus to prevent or reduce distribution of gravel past the bridge.
To alleviate the problem of bridging in gravel packing, shunt tubes have been used as alternate paths through which the gravel slurry can flow. Thus, if a sand bridge forms in the annulus, the slurry is still free to flow through the shunt tubes and out into the annulus through ports in the shunt tubes to complete the filling of the annulus past the sand bridge.
The shunt tubes may extend through a plurality of completion zones. As the annular region in each of the zones fill up with gravel, a point of "sand out" is reached in which further injection of gravel is prevented. At this point, any excess sand or other particulates in the production string may be circulated to the well surface. The well is then ready for production. However, the shunt tubes may remain in communication with multiple zones, which may cause commingling of formation fluids between zones. Such commingling of formation fluids is undesirable. Thus, a need exists for a method and apparatus to block communication of fluids between different zones through shunt tubes or other alternate conduits during production.